Tubular light source for a flow-type duplicating machine

ABSTRACT

A tubular light source for a flow-type duplicating machine provides an image with uniform brightness by making its luminousbrightness stronger around both its sides than around its middle along its longitude. A plurality of electrically conductive materials are disposed more densely in the middle portion of the light than around its end portions.

United States Patent [72] Inventors Masaya Ogawa' Osaka; Yorio Yamanoi, Toyokawa-shi, both of Japan [21 Appl. No. 798,394

[22] Filed Feb. 11, 1969 [45] Patented Nov. 30, 1971 [73] Assignee Minolta Camera Kabushiki Kaisha Osaka, Japan [32] Priority Feb. 15, 1968 [33] Japan [54] TUBULAR LIGHT SOURCE FOR A FLOW-TYPE DUPLICA'IING MACHINE 1 Claim, 3 Drawing Figs. v [52] U.S. Cl 355/67, 313/271, 313/274, 315/66 [51) Int. Cl. G03b 27/76 [50] Field of Search 355/67, 71, 88, 8, 3, 104; 313/1 17, 220,271, 274, 3; 315/65, 66

[56] References Cited UNITED STATES PATENTS 2,306,559 12/1942 Pearson 315/66 3,295,007 12/1966 315/66 3,435,286 3/1969 Kayatt 315/65 2,546,482 3/1951 Van Der Grinten 355/104 3,398,259 8/1968 Tregay et a1. 355/3 Primary Examiner-Samuel S. Matthews Assistant ExaminerRichard A. Wintercorn Almmey-Watson, Cole. Grindle & Watson ABSTRACT: A tubular light source for a flow-type duplicating machine provides an image with uniform brightness by making its luminous-brightness stronger around both its sides than around its middle along its longitude. A plurality of electrically conductive materials are disposed more densely in the middle portion of the light than around its end portions.

PATENTEDunvamsn 3,623,810

SHEET 2 0F 2 JAM $31427,

TUBULAR LIGHT SOURCE FOR A FLOW-TYPE DUPLICATING MACHINE BACKGROUND OF THE INVENTION The flow-type duplicating machine, either of ordinary photograph or of the electronic-type, works as follows. An original moves lengthways at a fixed speed across a slit-shaped opening, which is illuminated by a light source. The light from this illuminated original forms a slit-shaped image on an image-forming part by means of an image-forming optical system, and a photosensitive paper moves to be exposed at an image-forming part at the same fixed speed as the original. The time of exposure is fixed both by the intensity of illumination and by the speed of the moving original.

To reduce the time of this exposure, therefore, requires a bright light from the tubular light source to converge into a slit-shaped image on the opening by means of the illuminating optical system. When an original illuminated by this light forms a slit-shaped image on an image-forming part by means of an image-forming optical system, if the brightness is not unifonn longitudinally, the image formed on aphotosensitive paper is not exposed uniformly.

Generally speaking, however, with regards to an illuminating optical system or an image-forming optical system using lenses and reflex mirrors, because of its optical nature, the intensity of radiation at the end portions is inclined to become reduced resulting in underexposure of the corresponding end portions of the image. Especially this tendency is accelerated for a smaller duplicating machine. Accordingly, the abovementioned flow-type duplicating machine has such a defect as the intensity of radiation of the both sides of the slit-shaped image becomes reduced.

In order to cover this deficiency of the intensity of radiation around the both sides as above mentioned, a filter has been used as a means of absorbing light from the middle of a tubular light source. This way, however, does not only waste a portion of the energy from the light source, but also has a deleterious effect on the duplicating machine because the filter becomes heated by absorbing radiant rays from the light source.

SUMMARY OF THE INVENTION The first object of this invention is, in a flow-type duplicating machine, to eliminate the existing defects as before mentioned, and to unifonnly illuminate an original brightly which passes a slit-shaped illuminated opening. The object of this invention is to provide tubular light source having a luminousbrightness of both its sides stronger than that of its middle.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view of-the vertical section of one example of a flow-type electrostatic duplicating machine.

FIG. 2 is a sectional front view of the illuminative device, which is used in the above example and is one of the preferred embodiments of this invention, showing the inner part of the tubular light source.

FIG. 3 is a sectional front view of. another preferred embodiment of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. I, an original and a photosensitive paper are inserted one over the other from the inlet plate 2 installed at the insert opening I, and are separated by the separating plate 3 installed at the inlet plate 2. Then the original is transported linearly towards outlet opening 5 by feeding rollers 4a, 4b, and 40, while the photosensitive paper is fed, forming a hyperbolic curve in the machine,towards the photosensitive outlet opening 7 by the photosensitive feeding rollers 6a, 6b, 6c, 6d and 6e. As to the original, its relative position to the photosensitive paper is regulated by the regulator 8 between the rollers 4a and 4b, and it passes the opening 9 between the rollers 4b and 4c.

The photosensitive paper is electrically charged by the charging device 10 between the rollers 6a and 6b, and exposed to the light at the image-forming part 11 between the rollers 6b and 60. This exposed paper, thereafter, is developed through the developing bath 12 between the rollers 60 and 6d, and is issued after being dried by the drier between the rollers 6d and 6e.

The slit-shaped opening 9 is illuminated by the illuminating device 14, and the reflected light from the illuminated original, which moves while being pressed tightly onto the original registering glass plate 15 by the original-holding member 16, enters into the lense 18 by means of the first reflex mirror 17. And this light is reflected by mirror 19, and again passes through the lense l8, and is reflected by the second reflex mirror 20. Then this light forms a slit-shaped image on the photosensitive paper which moves while being pressed tightly onto the photosensitive paper registering glass plate 2! installed at the image part 11 by the photosensitive paper-holding member 22.

In such a process, as before mentioned, around both ends of the slit-shaped image-forming part which meets at right angles with the paper in FIG. 1, its intensity of radiation is reduced because of the optical nature of the illuminating optical system and an image-forming optical system as previously discussed.

This invention corrects this defect and provides a uniform brightness of the whole slit-shaped image in the following way. That is, as in shown in FIG. 2, in the tubular light source 24, which is located near the focus line of the cylindrical curvedsurface reflex mirror 23 at the brightness of its both sides 25 strengthened and that of its middle 26 weakened.

To make such tubular light source 24 as above, in the first preferred embodiment which is shown in FIG. 2, a coil filament 28 is set longitudinally in the transparent tubular bulb 27 of the tubular light source 24, and its both terminals are connected with a source of electricity. The coil filament 28 is wound densely around both end portions 29 and sparsely around the middle portion 30. 31 is a ring to support the filament 28 correctly at approximately the center of the tubular bulb 27, and several of such rings are installed there.

The second preferred embodiment of this invention is shown in FIG. 3. The coil filament 32 wound with substantially uniform pitch is used as a luminous filament disposed longitudinally in the tubular light source, and several short thermostable electrically conductive materials 33 are inserted in this coil. The filament of the parts where these materials are inserted is shorted to be nonluminous. These thermostable electrically conductive materials 33 are inserted in the coil sparsely around both end portions 34 of the filament 32 and densely around the middle 35 of it.

In a tubular light source; the parts of the luminous filament 32 where no thermostable electrically conductive material 33 is inserted, radiate almost uniformly, while the brightness of the middle 35, where the nonluminous parts of the thermostable electrically conductive materials 33 are densely located, is weaker than that of the both sides 34 where these materials are thinly located.

This phenomenon counterbalances the reduction of the intensity of radiation around the end portions which is a characteristic of both an illuminating optical system and an imageforming optical system, and consequently it becomes possible to form the image having the uniform brightness on the slitshaped image-forming part II.

What is claimed is:

1. A flow-type duplicating machine, comprising;

means for illuminating a moving document and including an elongated aperture extending transverse to the direction of movement of said document,

means for exposing said illuminated document onto moving photosensitive paper and including an elongated aperture extending transverse to the direction of movement of said photosensitive paper,

illuminating device 14, has the v means for projecting an image of said illuminated document from said means for illuminating to said means for exposing,

a tubular light source mounted adjacent to said means for illuminating having a longitudinal axis parallel and transverse to the direction of movement of said document, said tubular light source including a tubular globe, electrodes mounted at both ends of said tubular globe, a helically wound coil filament having substantially equal coil pitch along its length and extending between said electrodes, 

1. A flow-type duplicating machine, comprising; means for illuminating a moving document and including an elongated aperture extending transverse to the direction of movement of said document, means for exposing said illuminated document onto moving photosensitive paper and including an elongated aperture extending transverse to the direction of movement of said photosensitive paper, means for projecting an image of said illuminated document from said means for illuminating to said means for exposing, a tubular light source mounted adjacent to said means for illuminating having a longitudinal axis parallel and transverse to the direction of movement of said document, said tubular light source including a tubular globe, electrodes mounted at both ends of said tubular globe, a helically wound coil filament having substantially equal coil pitch along its length and extending between said electrodes, and several thermostable electroconductive rods inserted between individual ones of said coil windings for electrically shorting the interconnected windings, said electroconductive rods are spaced from each other and more densely distributed in the central portion of said coil filament than at the end portions thereof whereby the illumination intensity of said light source is substantially uniform. 